In the automated conveyor art, one type of automatic conveyor system is known as an accumulator conveyor. These types of conveyors are divided into a plurality of zones that extend from an inlet end to a discharge end. The zones are areas of the conveying surface where driving force to move the packages may be applied or removed independently of the other zones of the conveyor. These zones provide each package with its own stopping place. Packages or items are thus accumulated in successive zones for eventual discharge from the conveyor.
Zero pressure accumulation is a method of accumulating one or more items on a conveyor in a manner wherein there is no drive pressure or force trying to move the accumulated item before it is ready to be conveyed into another zone or discharged from the conveyor. Zero pressure accumulation conveyors differ from minimum pressure accumulation conveyors in that with minimum pressure conveyors there is always some drive pressure on the packages, even when the packages are being accumulated. Generally, each zone includes a sensing mechanism to determine whether a package is within its zone and associated logic to activate or deactivate the zone's driving force. Such sensors may be mechanical, or may be photoelectric.
However, while there are known electronic sensing systems such as that shown and described in U.S. Pat. No. 5,060,785 entitled Electrically-Powered Control System For Accumulating Conveyor issued to Garrity on Oct. 29, 1991, and U.S. Pat. No. 5,285,887 entitled Accumulating Conveyor And Control System issued to Hall on Feb. 15, 1994, they are deficient in many respects. Furthermore, these systems are not flexible in terms of options, wiring, or the like.
It is thus an object of the present invention to provide an improved control system for an accumulating conveyor.
It is another object of the present invention to provide a control system for an accumulating conveyor that provides photo-electric sensing at nearly the same cost as conventional mechanical/pneumatic sensing.
It is yet another object of the present invention to provide a control system for an accumulating conveyor which requires few parts and is simple to wire.
It is further an object of the present invention to provide a control system for an accumulating conveyor that has a higher degree of reliability than conventional mechanical/pneumatic control systems.
It is still further an object of the present invention to provide an accumulating conveyor control system that has several modes of operation, and offers greater flexibility than mechanical and/or pneumatic accumulation logic.